This study will examine the natural history of patient compliance following renal transplantation and identify associations between noncompliance and discrete transplant outcomes. The grant aims are: 1) To define and prospectively quantify compliance in a population of renal transplant recipients; 2) To characterize correlations between noncompliance and clinically relevant outcomes (death, graft loss, rejection, and infection); 3) In conjunction with projects Id2 and Id3 to identify predictors of compliance and evaluate compliance interventions. The primary quantitative estimate of posttransplant regiment compliance will be opening the immunosuppressive medication container. This will be recorded by electronic micro-circuitry in the bottle cap. Azathioprine metabolites will also be investigated as compliance markers and correlated with the electronic monitor. Three patient groups will be studied prospectively, an inception cohort (n=200) composed of unselected patients having just received a renal transplant and two cross-sectional cohorts of patients reaching their second (n=200) or fourth (n=180) transplant anniversary with a functioning renal graft. The inception cohort will be followed for up to 5 years, while the cross-sectional cohorts will be followed 2 years. These studies will yield the first extensive data on patient noncompliance including its incidence and prevalence over the 6 year interval after renal transplantation. Prospective compliance data will be correlated with defined patient end- points, including biopsy-proven rejection, graft loss, and patient death. For each end-point, the relative risk contributed by noncompliance will be estimated with the Cox regression model. Data from this study will be combined with data from the companion compliance studies (Id2 and Id3) to expand the picture of patient compliance following transplantation. Characteristics predictive of patient compliance will be defined, allowing focused interventions to improve compliance. Finally, compliance monitoring techniques developed in this study will be applied to objectively quantitate compliance and its improvement in the intervention studies proposed in Id3.